兵勢

分數 — 'organisation,' literally 'division and numbering.' This refers to the hierarchical subdivision of forces into squads (伍), companies (百), and larger units, so that commands flow smoothly regardless of total army size.

形名 — 'signals and formations,' literally 'forms and names.' 形 here refers to visual signals (flags, banners, formations); 名 refers to auditory signals (drums, gongs, verbal commands). Together they are the command-and-control system.

奇正 (qi zheng) — 'the unorthodox and the orthodox.' 正 is the main body that engages the enemy frontally (the pinning force); 奇 is the flanking or surprise element that delivers the decisive blow. This paired concept is central to classical Chinese military thought.

虛實 (xu shi) — 'emptiness and fullness.' Where the enemy is empty (dispersed, undefended, weak), you strike with fullness (concentrated, prepared, strong). This is the subject of Chapter 6.

碫 (duan) — a grindstone or whetstone. Some editions write 碬. The image: a heavy stone dropped on an egg — the disproportion is total.

五聲 (five notes) — the Chinese pentatonic scale: gong (宮), shang (商), jue (角), zhi (徵), yu (羽), roughly corresponding to C, D, E, G, A.

五色 (five colours) — blue-green (青), red (赤), yellow (黃), white (白), black (黑). These correspond to the Five Phases (wuxing) system.

五味 (five tastes) — sour (酸), bitter (苦), sweet (甘), pungent (辛), salty (鹹).

以正合以奇勝 — 'the orthodox engages, the unorthodox achieves victory.' This is arguably Sunzi's most compressed tactical formula. 合 means to close with, to engage, to fix in place; 勝 means to prevail. The orthodox force pins the enemy; the unorthodox force delivers the killing blow.

Sunzi's analogy to music, colour, and taste demonstrates a combinatorial logic: from a finite set of elements, infinite variations arise. The skilled commander does not need exotic tactics — only the ability to recombine orthodox and unorthodox in novel ways.

勢 (shi) — 'momentum' or 'strategic advantage.' This is the chapter's title concept. 勢 is the dynamic, positional energy that arises from proper arrangement of forces — like water that has been dammed or a crossbow that has been drawn. It is potential energy on the verge of release.

節 (jie) — 'timing,' literally 'the joint' or 'the node.' In the crossbow metaphor, it is the trigger mechanism (發機) — the precise instant of release. The word conveys both brevity (the strike window is short) and precision (it must hit the exact right moment).

險 (xian) — 'steep,' 'precipitous,' here rendered 'overwhelming.' The metaphor is topographic: momentum builds like water at the edge of a cliff. 短 (duan) — 'short,' meaning the window of release is compressed.

彍弩 (kuo nu) — a crossbow drawn to full tension. The crossbow was a transformative weapon in Warring States warfare, allowing massed volleys of bolts from trained infantry. Sunzi uses it as a metaphor for accumulated force waiting for the precise moment of release.

鷙鳥 (zhi niao) — a raptor, specifically a hawk or falcon. 毀折 — 'to break and shatter.' The bird's strike kills not by weight but by timing: it dives at the exact moment when its velocity, angle, and the prey's vulnerability all align.

紛紛紜紜 and 渾渾沌沌 are reduplicated binomes evoking the sensory chaos of battle — the visual confusion of flags, dust, and surging troops. These onomatopoeic expressions resist precise translation; they convey overwhelming sensory disorder.

形圓 — 'form is round/circular,' meaning the formation has no exposed flanks, no weak point to attack from any direction. A circular formation can respond equally to threats from any quarter.

亂生於治 — 'disorder arises from order.' This is a key Sunzi principle: you can only deploy apparent disorder as a tactic if you have real discipline underneath. Feigned chaos used to lure the enemy into a trap requires iron control. The same logic applies to apparent cowardice (a feigned retreat) and apparent weakness (a deceptive show of vulnerability).

數 (shu) — here means 'organisation' or 'structural division' (the same concept as 分數 in section 1). 勢 (shi) — momentum/strategic advantage. 形 (xing) — disposition/form. These three terms correspond to the three pairs: order/disorder depends on how you organise; courage/cowardice depends on the momentum you generate; strength/weakness depends on how you deploy your forces.

形之 — 'shape it' or 'show a form to him.' The verb 形 here means to create a visible disposition that the enemy is forced to react to — a feint, a false deployment, a deceptive show of force. The enemy 'must respond' (必從之) because he cannot afford to ignore the apparent threat.

予之 — 'offer something to him.' This is the bait: a seemingly vulnerable position, an apparently abandoned supply depot, a gap in the line. 敵必取之 — the enemy must seize it, because the temptation is irresistible.

以卒待之 — 'wait for him with troops.' 卒 here means soldiers/troops. Some commentators read 卒 as 'suddenly' (zu), giving 'wait for him with sudden action,' but the parallel with 以利動之 (move with advantage) favours reading 卒 as troops.

求之於勢不責於人 — 'seeks it in momentum, does not demand it from men.' This is Sunzi's most explicit statement of the chapter's thesis: a good commander does not rely on individual heroism or blame his soldiers for failure. He creates structural conditions — momentum — that make victory almost automatic.

擇人而任勢 — 'selects men and exploits momentum.' 擇 means to choose carefully; 任 means to employ or rely on. The commander's job is twofold: pick the right people for the right roles, then create the momentum that carries them to victory.

The chapter ends with the same image that closed Chapter 4 — water/stones cascading down from a height of a thousand ren. But where Chapter 4 used the metaphor of releasing dammed water (形, form/disposition), Chapter 5 uses the metaphor of a rolling stone (勢, momentum). Disposition is the static arrangement; momentum is the dynamic energy released from that arrangement.

方則止圓則行 — 'if square they stop, if round they roll.' This is both literal physics and metaphor: the commander's job is to make his forces 'round' — adaptable, mobile, without corners that catch — so that momentum carries them forward irresistibly.